Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Alzheimer's Blood Test a 'Major' Step Closer: Study

A major advance has been made in creating a blood test to predict when at-risk people will develop Alzheimer's disease, according to scientists.

In a study that included more than 1,000 people, the British researchers identified proteins in the blood that were 87 percent accurate in forecasting which people with mild cognitive impairment would develop Alzheimer's within a year, BBC News reported.

The findings, published in the journal Alzheimer's and Dementia, will be used to improve studies of new drugs to treat Alzheimer's.

"We want to be able to identify people to enter clinical trials earlier than they currently do and that's really what we've been aiming at," lead researcher Professor Simon Lovestone, University of Oxford, told BBC News.

However, the test may eventually be available for doctors to use on patients.

"[It] will take several years and need many more patients before we can be certain these tests are suitable for routine clinical use, that process can start fairly quickly now," he added.

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Researchers Switch Woman's Consciousness On and Off

It may be possible to turn a person's consciousness on and off, a new study case suggests.

Researchers implanted electrodes in the brain of 54-year-old woman with epilepsy in order to pinpoint the part of the brain that was causing her seizures. One of the regions they tested was the claustrum, a thin layer of neurons connected to the neocortex center of the brain, CBS News reported.

When the scientists applied electrical stimulation to the claustrum, the woman went into state of unconsciousness. When the stimulation was turned off, she returned to a normal state of consciousness and did not remember what had just happened.

The study was published in the journal Epilepsy and Behavior.

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Close Foster Farms Until Salmonella Outbreak Over: Lawmakers

All Foster Farms poultry plants should be closed down until a salmonella outbreak that has sickened more than 600 people is confirmed to be over, two members of Congress say.

Since March 2013, at least 621 people in 29 states and Puerto Rico have been sickened by salmonella linked to chicken produced by California-based Foster Farms, NBC News reported.

The call for the company to be shut down until the outbreak is resolved was made Monday by Rep. Rosa DeLauro, D-Conn., and Rep. Louise Slaughter, D-N.Y., who have introduced a bill that would make food recalls mandatory during such outbreaks.

The lawmakers made their demand for Foster Farms to be closed after a July 3 announcement that the company was voluntarily recalling all chicken parts produced during several days in March, and a July 4 Centers for Disease Control and Prevention update about how many people have been sickened in the outbreak.

The USDA and Foster Farms refused to reveal how many pounds of chicken were recalled on July 3, saying only that it was an "undetermined amount," NBC News reported.

USDA Food Safety and Inspection Service officials said until now, they weren't able to confirm a direct link between Foster Farms chicken and the salmonella outbreak. They also said they have no authority to issue a mandatory recall of Foster Farms chicken or to close the company's plants.

However, federal officials did order a shutdown last winter after they discovered cockroaches at a Foster Farms plant, NBC News reported.

"How many more people will fall ill, or even be hospitalized, before USDA does the right thing and cracks down on companies that threaten our families' health and safety?" DeLauro and Slaughter said.